Cascade Saddle is still a viable option – West Matukituki Valley, Cascade Saddle, Dart Hut, Rees Saddle, Rees Valley, Muddy Creek (and so avoid the Dart landslip). However, a warning needs to be given – the climb to Cascade Saddle from the WM valley is exposed and dangerous, especially in wet/snow conditions.
digbyg wrote: We have done ... copland crossing ...
However, if you mean the Copland Track (the classic mountaineering route between Mount Cook and the West Coast) then Cascade Saddle would not be a problem.
Assuming you are looking for something lest structured than a Great Walk, there are many options in the Kahurangi NP (top of the SI).
A good recognised tramp is the Travers-Sabine loop. Alternatively, a 100km through tramp with some less travelled sections have a look at St Arnaud to Lewis Pass
http://tramper.co.nz/?8459 – so many choices !